fix(security): deliver the hook secret to hooks + isolate its rate-limit bucket

Review fixes for COD-54:

- Generated hook curl commands now present X-Codeman-Hook-Secret, read from
  the secret file AT EXECUTION TIME via $CODEMAN_HOOK_SECRET_FILE (exported
  into every managed session's env by tmux buildEnvExports / the direct-PTY
  env builders). Without this, every local hook 401'd the moment a managed
  tunnel came up — the enforcement existed but nothing presented the secret.
  Path-not-value keeps the secret off command lines and out of config files,
  and running sessions pick up a newly generated secret with no respawn;
  server.start() ensures the file exists up front.

- Hook-secret failures now count into a DEDICATED per-IP bucket
  (hookSecretFailures) instead of the shared authFailures map. Legacy
  (pre-secret) hook configs fire constantly from 127.0.0.1; counting their
  401s against the shared bucket would 429 every cookie-less loopback
  request — locking out the Basic-Auth login path (and, through a tunnel,
  every client, since tunneled traffic also arrives as 127.0.0.1).

- docs/security-architecture.md: secret-gated hook exemption, dedicated
  bucket, COD-55 refusal, and the residual caveat for EXTERNAL loopback
  proxies (user-run cloudflared / tailscale serve), which the
  managed-tunnel probe cannot see.

- test/cod54-hook-event-auth.test.ts: +3 tests — login path unaffected
  after hook-bucket exhaustion; generated hooks reference the header +
  $CODEMAN_HOOK_SECRET_FILE without embedding the value; env builders
  export the path only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/hooks-config.ts

@@ -3,8 +3,9 @@
  *
  * Generates `.claude/settings.local.json` with hook definitions that POST
  * to Codeman's `/api/hook-event` endpoint when Claude Code fires hooks.
- * Uses `$CODEMAN_API_URL` and `$CODEMAN_SESSION_ID` env vars (set on every
- * managed session) so the config is static per case directory.
+ * Uses `$CODEMAN_API_URL`, `$CODEMAN_SESSION_ID`, and `$CODEMAN_HOOK_SECRET_FILE`
+ * env vars (set on every managed session) so the config is static per case
+ * directory and free of secret values.
  *
  * Key exports:
  * - `generateHooksConfig()` — returns hooks object for settings.local.json
@@ -41,11 +42,18 @@ import { HOOK_TIMEOUT_MS } from './config/auth-config.js';
 export function generateHooksConfig(): { hooks: Record<string, unknown[]> } {
   // Read Claude Code's stdin JSON and forward it as the data field.
   // Falls back to empty object if stdin is unavailable or malformed.
+  // COD-54: present the per-instance hook secret so the bypass keeps working while
+  // a tunnel is running. The value is read from the secret file AT EXECUTION TIME
+  // (path via $CODEMAN_HOOK_SECRET_FILE, set in every managed session's env), so it
+  // never lands in this config and rotation needs no respawn. If the var/file is
+  // missing the header is empty — the middleware then allows the request only on
+  // the plain loopback bypass (tunnel down), same as pre-secret behavior.
   const curlCmd = (event: HookEventType) =>
     `HOOK_DATA=$(cat 2>/dev/null || echo '{}'); ` +
     `printf '{"event":"${event}","sessionId":"%s","data":%s}' "$CODEMAN_SESSION_ID" "$HOOK_DATA" | ` +
     `curl -s -X POST "$CODEMAN_API_URL/api/hook-event" ` +
     `-H 'Content-Type: application/json' ` +
+    `-H "X-Codeman-Hook-Secret: $(cat "$CODEMAN_HOOK_SECRET_FILE" 2>/dev/null)" ` +
     `--data @- ` +
     `2>/dev/null || true`;